Power sources such as radiation particle power converters can convert energy from a radioactive source that emits high-energy electrons, e.g., beta particles, into electrical energy. The power converter can directly convert the energy of the high-energy electrons to electrical energy, i.e., current, by collecting electron-hole pairs that are formed by the high-energy electrons that are incident upon a semiconductor material of the power converter.
One such direct power source includes a radiation-emitting radioisotope and a plurality of semiconductor substrates. Each of the plurality of semiconductor substrates includes a junction for converting radiation particles to electrical energy, e.g., a p-n junction. The junction collects electron-hole pairs that are created within the semiconductor material as a result of interaction with the nuclear radiation particles. Specifically, when a radiation particle of sufficient energy impacts the semiconductor material, electrons in the semiconductor material are excited into a conduction band of the semiconductor material, thereby creating electron-hole pairs. Electrons formed on an n side of a p-n junction are generally prevented from crossing the p-n junction due to the electric field that is created in a depletion zone, while the corresponding holes are swept across the p-n junction by the electric field. Electrons formed on the p side of the p-n junction are swept across the junction by the electric field while the corresponding holes are prevented from crossing the junction by the electric field. When the semiconductor material is connected to a load, electrons formed on the n side of the junction are swept across the junction from the p side via an anode and through a circuit connected to the power converter. The electrons that flow through the circuit then flow into the p side via a cathode, where they can recombine with holes from the original electron-hole pairs.
Other types of power sources that utilize radiation particles indirectly convert the particles by utilizing a phosphor layer placed adjacent the radiation particle source. The phosphor absorbs the energy of the radiation particles and emits visible or invisible light, which is absorbed and converted into electricity by a photovoltaic device. While such indirect power sources may initially be less efficient than direct power sources, over time such indirect power sources have a higher efficiency and longer service life than that of at least some of the direct power sources.